Early Preplant Atrazine and Metolachlor in Conservation Tillage Corn (Zea mays)

Abstract

Field research was conducted at Arlington, WI in 1984 and 1985 to determine the influence of application timing on weed control with atrazine and metolachlor in conservation tillage corn production systems. Early preplant treatments controlled fewer weeds than preemergence or early preplant/preemergence sequential treatments in a chisel plow system. Velvetleaf control was only 50% late in the growing season with early preplant atrazine compared with 88% with an early preplant/preemergence sequential treatment of the same amount of atrazine. In the no-till system, early preplant applications of atrazine and/or metolachlor had reduced weed control late in the growing season compared with preemergence and early preplant/preemergence sequential treatments of the same amount of herbicide. Giant foxtail control 110 d after corn planting was only 73% with an early preplant treatment compared with 99% when the same amount of herbicide was evenly divided between early preplant and preemergence applications.